Conficker was believed to be the worst computer worm since the SQL slammer worm in 2003.[5] It was estimated 15 million computers were infected with Conficker.[6][7] The virus was supposed to get worse on April 1, 2009, which caused many people to worry about it. However there were no bad effects.[8]

On 13 February 2009, Microsoft offered a $250,000 USD reward for help with finding and arresting the people who created the computer worm.[9][10][11][12][13]